This invention relates to the detection of the position and orientation of a reference beam of light and, more particularly, to an apparatus for detecting the position and attitude of an excavation or boring machine with respect to such a beam to permit an operator to make timely corrections for any deviations in the path of the machine from its proper course.
Excavation and earth boring machines are known. These machines tunnel beneath the earth and are useful for laying large underground pipelines and for tunneling through mountains and/or beneath rivers and the like. Such machines are quite large, typically having a diameter in the range of 20 to 50 feet and a length several times that. It is necessary to control the direction of movement of an excavation machine rather precisely, however, so that the machine follows a proper, predetermined course. Once an excavation machine veers off course significantly, returning it to its desired path is somewhat difficult.
One prior system for controlling the direction of such excavation machinery involves the use of a laser beam or other beam of coherent light which is aimed along the desired machine path. A target for the beam, mounted on the rear of the machine is watched by the machine operator. If the excavation machine veers off course, this fact is indicated by the beam of light moving off of the center of the target. The operator then corrects the direction of the machine until the beam of light impinging the target indicates that the machine is back on its proper course.
The problem with this prior system is that, although it indicates when the rear end of the machine is properly positioned, most excavation machines have the boring mechanism located on the front of the machine, which is a substantial distance from the rear of the apparatus. Thus, the prior system was incapable of detecting the attitude or orientation of the excavation machine. That is, although the beam of light might indicate that the rear of the machine was directly on target, the front of the machine could be out of alignment significantly either in the vertical direction (pitch) or the horizontal direction (yaw). The task of the operator in controlling the direction of such a machine is made more difficult in that the machine is controlled from a station near its rear end where the attitude of the machine is not readily apparent to the operator. For example, if the front of the excavation machine were digging at too steep a grade, this would not be apparent until eventually the position of the beam of light on the target would alert the operator to this fact. The operator could make the necessary corrections to the course of the machine but the machine most likely would already be substantially off course. Thus the prior art system tended to cause the operator to overcorrect, leading to the need for further corresponding changes in the direction of the machine.
Accordingly, there is a need in the art for an apparatus which can measure the relative position and the relative orientation of a reference beam of light, which information can then be utilized to determine the orientation and attitude of an excavation or earth boring machine to provide improved control.